Method for identifying a cause of blockage in a sequence of images, a computer program for performing said method, a computer-readable recording medium containing such computer program, a driving assistance system capable of executing said method

Abstract

A method for identifying a cause of blockage in a sequence of images provided by a camera of a vehicle, the method comprising iteratively performing steps of:S10) acquiring an image of the camera; successively acquired images thus forming said sequence of images;S20) detecting a blockage in last images of the sequence of images;S60) determining whether it is day-time or night-time based on time information;S70) if it is determined that it is day-time,S72) determining whether outside temperature is below a low temperature threshold, and if it is the case,S73) determining that for the current iteration, the cause of the blockage is presumably icing or fogging.A computer program for performing said method, a computer-readable recording medium containing such computer program, a driving assistance system capable of executing said method.

1 . A method for identifying a cause of blockage in a sequence of images provided by a camera mounted in a vehicle which is moving on a road, the method comprising iteratively performing steps of:
 S 10 ) acquiring an image of the camera; successively acquired images thus forming said sequence of images;   S 20 ) detecting a blockage in last images of the sequence of images;   S 60 ) determining whether it is day-time or night-time based at least on time information;   if it is determined that it is day-time, performing a step S 70  comprising:   S 72 ) determining whether outside temperature is below a low temperature threshold;   S 73 ) if it is determined that the outside temperature is below the low temperature threshold, determining that for a current iteration, the cause of the blockage is presumably icing or fogging.   
     
     
         2 . A method for identifying a cause of blockage according to  claim 1 , wherein the method further comprises, at step S 70 , if it has been determined at step S 72  that the outside temperature is below the low temperature threshold, performing the steps of:
 S 74 ) determining whether dew point is reached; 
 if it is determined that the dew point is not reached, determining that for the current iteration, the cause of the blockage is presumably icing or fogging with a first probability (P 1 ); 
 S 75 ) if it is determined that the dew point is reached, determining that for the current iteration, the cause of the blockage is presumably icing or fogging with a second probability (P 2 ) which is higher than the first probability (P 1 ). 
 
     
     
         3 . A method for identifying a cause of blockage according to  claim 1 , wherein the method further comprises, at step S 70 , performing the step of:
 S 78 ) if it is determined that the outside temperature is above the low temperature threshold, determining that for the current iteration, the cause of the blockage is presumably a sunset/sunrise situation or a uniform landscape situation.   
     
     
         4 . A method for identifying a cause of blockage according to  claim 1 , wherein the method further comprises, if, during an iteration, it is determined at step  60  that it is night-time, performing step S 80  of:
 S 82 ) determining whether toggling front light(s) of the vehicle on/off causes a change in images acquired by the camera; and 
 S 84 ) if it is determined that toggling front light(s) on/off causes a change in said images acquired by the camera, determining that for the current iteration, the cause of the blockage is presumably the road being dark. 
 
     
     
         5 . A method for identifying a cause of blockage according to  claim 1 , wherein the method further comprises, during an iteration, before performing step S 60 , performing steps of:
 S 40 ) detecting lane markings in a last image of the sequence of images; and   S 45 ) if lane markings are detected in the last image, returning to step S 10  of image acquisition.   
     
     
         6 . A method for identifying a cause of blockage according to  claim 5 , wherein the method further comprises, during an iteration, before performing step S 40 , performing steps of:
 S 30 ) determining whether a lane on which the vehicle moves has lane markings, based on position information of the vehicle and a database comprising records of lanes having lane markings; and   S 35 ) if a lane on which the vehicle moves does not have lane markings, returning to step S 10  of image acquisition.   
     
     
         7 . A method for identifying a cause of blockage according to  claim 1 , wherein the method further comprises, during an iteration, before performing step S 60 , performing steps of:
 S 50 ) detecting whether there is an object on the road in front of the vehicle, based on information other than information derived from the images;   S 55 ) if no object is detected on the road in front of the vehicle, returning to step S 10  of image acquisition.   
     
     
         8 . A method for identifying a cause of blockage according to  claim 1 , wherein the method further comprises, when, during an iteration, a first cause of blockage has been detected, performing the steps of:
 S 90 ) assessing whether a blockage has been detected at least for each of last N1 iterations, and assessing whether the cause of the blockage has been determined to be presumably said first cause for at least N2 iterations during the last N1 iterations, N1 and N2 being predetermined numbers; and   S 110 ) if a blockage has been detected at least for each of last N1 iterations, and the cause of the blockage has been determined to be presumably said first cause for at least N2 iterations during the last N1 iterations, triggering an action based on the determination that the cause of the blockage is said first cause.   
     
     
         9 . A method for identifying a cause of blockage according to  claim 1 , wherein the images are partial images which are part of larger images acquired by the camera. 
     
     
         10 . A computer program which is stored on a computer readable storage media, and which is suitable for being performed on a computer, the program including instructions adapted to perform the steps of a method according to  claim 1  when it is run on the computer. 
     
     
         11 . A computer-readable recording medium including instructions of a computer program according to  claim 10 . 
     
     
         12 . A driving assistance system, comprising an electronic control unit ( 22 ), a camera ( 30 ), an outer temperature sensor ( 34 ), the electronic control unit ( 20 ), the camera ( 30 ) and the outer temperature sensor ( 34 ) being configured to be mounted in a vehicle; wherein the electronic control unit ( 20 ) is configured to iteratively:
 S 10 ) acquire an image of the camera ( 30 ); successively acquired images thus forming said sequence of images;   S 20 ) detect a blockage situation in last images of the sequence of images;   S 60 ) determine whether it is day-time or night-time based at least on time information; and if the electronic control unit has determined that it is day-time:   S 72 ) determine whether outside temperature is below a low temperature threshold and dew point is reached, based on information provided by the outer temperature sensor; and,   S 73 ) if the electronic control unit has determined that the outside temperature is below a low temperature threshold, determine that for a current iteration, the cause of the blockage is presumably icing or fogging.   
     
     
         13 . A driving assistance system according to  claim 12 , further comprising a humidity sensor ( 32 ), and wherein the electronic control unit is further configured:
 S 74 ) to determine whether dew point is reached;   if the electronic control unit has determined that the outside temperature is below the low temperature threshold and that the dew point is not reached, to determine that for the current iteration, the cause of the blockage is presumably icing or fogging with a first probability (P 1 ); and   S 75 ) if the electronic control unit has determined that the outside temperature is below the low temperature threshold and that the dew point is reached, to determine that for the current iteration, the cause of the blockage is presumably icing or fogging with a second probability (P 2 ) which is higher than the first probability (P 1 ).   
     
     
         14 . A driving assistance system according to  claim 12 , wherein the electronic control unit is further configured:
 S 78 ) if the electronic control unit has determined that the outside temperature is above a low temperature threshold, to determine that for a current iteration, the cause of the blockage is presumably a sunset/sunrise situation or a uniform landscape situation.   
     
     
         15 . A driving assistance system according to  claim 12 , wherein the electronic control unit is further configured, if, during an iteration, the electronic control unit ( 20 ) has determined that it is night-time:
 S 82 ) to determine whether toggling front light(s) of the vehicle on/off causes contrast change in the images; and   S 84 ) if the electronic control unit has determined that toggling front light(s) on/off causes contrast change in the images, to determine that for the current iteration, the cause of the blockage is presumably the road being dark.   
     
     
         16 . A driving assistance system according to  claim 12 , wherein the electronic control unit is further configured, during an iteration, before determining whether it is day-time or night-time:
 S 40 ) to detect lane markings in a last image of the sequence of images; and   S 45 ) if at least one lane marking is detected in the last image, to return to step S 10  of image acquisition.   
     
     
         17 . A driving assistance system according to  claim 12 , wherein the electronic control unit is further configured, during an iteration, before determining whether it is day-time or night-time:
 S 50 ) to detect whether there is an object on the road in front of the vehicle, using environment information other than information derived from the images;   S 55 ) if the electronic control unit has detected that there is an object on the road in front of the vehicle, to return to step S 10  of image acquisition.   
     
     
         18 . A automated driving system according to a  claim 12 , wherein the electronic control unit is further configured, when, during an iteration, a first cause of blockage has been detected:
 S 90 ) to assess whether a blockage has been detected at least for each of last N1 iterations, and to assess whether the cause of the blockage has been determined to be presumably said first cause for at least N2 iterations during the last N1 iterations, N1 and N2 being predetermined numbers; and, S 110 ) if a blockage has been detected at least for each of the last N1 iterations, and the cause of the blockage has been determined to be presumably said first cause for at least N2 iterations during the last N1 iterations, to trigger an action based on the determination that the cause of the blockage is the first cause.